Mechanism for locking the keyboard of electric typewriters or like machines



1957 T. N. MADISON ETAL MECHANISM FOR LOCKING THE KEYBOARD OF ELECTR TYPEWRITERS OR LIKE MACHINES Filed Dec. 2, 1965 INVENTORS THEODORE N. MADISON ROBERT E. Mc GRATH ATTORNEYS United States Patent MECHANISM FOR LOCKING THE KEYBOARD 0F ELECTRIC TYPEWRITERS 0R LIKE MACHINES Theodore N. Madison, Thompsonville, and Robert E.

McGrath, Wethersfield, Conn., assignors to Royal Typewriter Company, Inc., New York, N.Y., a corporation of Delaware Filed Dec. 2, 1965, Ser. No. 511,166

6 Claims. (Cl. 197-107) ABSTRACT OF THE DISCLOSURE A mechanism for locking the keyboard of electric typewriters and the like having a key lever locking blade movable between first and second positions to respectively block and permit depressions of key levers associated with type actions, and means for moving said locking blade into and to maintain said locking blade in said second position in response to forward rotation of a shaft powering the typewriter and to move said locking blade into said first position upon cessation of forward rotation of the shaft powering the typewriter.

This invention relates to mechanism for locking the keyboards of electric typewriters or like machines; more particularly it relates to keyboard lock mechanism characterized by a locking blade operable to unlock the keyboard incident to motor operation and to lock the keyboard when motor operation ceases.

In the prior art exemplified by Patent 2,945,577, motor power is utilized to unlock the keyboard and electromagnetic power is utilized to maintain the keyboard unlocked during machine operation. The electromagnet employed represents a higher manufacturing as well as a higher operating cost.

In accordance with the present invention motor power is employed in a novel manner to operate the locking blade to unlocked condition and to maintain it in unlocked condition as well, thus obviating the necessity for an electromagnet. When motor operation ceases as a result of power termination the energy stored in a spring during motor operation is employed to restore the locking blade to locked condition.

A further feature of the invention resides in the fact that service function key actions which are generally not locked out with the type function key levers and characterized by wrap spring clutches energizable to couple power to associated instrumentalities, as, for example, carriage return and backspace, are automatically disable-d simultaneously with the movement of the locking blade to locked condition.

Accordingly, an object of the invention is to provide an improved low cost keyboard locking mechanism in an electric typewriter.

Another object of the invention is to provide a keyboard lock mechanism movable to and maintained in an unlocked condition in response to motor power.

Still another object of the invention is in the provision of mechanism responsive to motor power to unlock a typewriter keyboard and responsive to motor power stored in a spring to restore the keyboard to locked condition when motor power is terminated.

A further object of the invention is in the provision of mechanism utilizing stored motor power to operate a keyboard locking blade to lock position and to reversely rotate a power roll thereby to prevent the tripping or energization of clutches associated with service function keys not locked out by said locking blade.

Other objects and many of the attendant advantages of 3,349,886 Patented Oct. 31, 1967 this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughtout the figures thereof and wherein:

FIGURE 1 is an elevational view showing mechanism in accordance with the invention in keyboard lock (motor ofi) condition;

FIGURE 2 is a perspective view of the mechanism controlled by the motor and operable on the locking blade in keyboard lock condition; and

FIGURE 3 is a partial elevational view of the motor controlled locking mechanism in keyboard unlock (motor on) condition.

Referring now to the drawings wherein like reference numerals designate like or corresponding elements throughout the several views and wherein a preferred embodiment is illustrated, there is shown in FIGURE 1 a key lever 11 comprising one of a complement of type iaction key levers operable upon depression to rock an action trip lever 12 clockwise and thus to rock an eccentric cam 13, pivoted on a sub-lever 14, into engagement with a power roll 15 whereupon the sub-lever will be driven forwardly or counterclockwise as viewed in the figum and by means of a link drive a type bar 16 to printing position on the platen 3 driven by pressure rollers 5 and 6.

All of the type action key levers 11 extend forwardly so that notches 17 on the underside overlie, in the machine oif condition shown, the upper edge of a key lever locking blade 18 which extends across the machine and is pivotally mounted at its lower edge on frame mounted studs 19.

As viewed in FIGURE 1 a motor driven shaft 21 is caused to rotate in a clockwise or forward direction upon closure of a switch responsive to manipulation of an onoff lever to the on position. The motor driven shaft 21 drives a pulley 22 which is operably connected as by a belt 23 to a speed reducing pulley 24 secured to the shaft 25 carrying the typewriter power roll 15. Preferably the belt and pulleys are toothed. Rotatably mounted intermediate its end on the motor driven shaft 21 is a locking lever 26. A normally gripping wrap spring 27 is also wound on motor driven shaft 21, as viewed from the right end, in a clockwise direction in the direction of motor rotation. The right end 28 of the wrap spring is bent axially and secured to the upper arm of the lever and the left end 29 of the spring is bent outwardly and extends forwardly into a slot 31 of a frame supported member 32; the slot defining upper and lower spaced abutments. The lower arm of the lever is connected as by a link 33 to a slotted tab 34 located on the type lever action locking blade 18 above the pivots thereof. A locking lever biasing spring 35 is secured between the frame member 32 and the upper arm of lever 26. Should forward rotation of the motor shaft 21 be stopped deliberately by manipulation of the on-olf key to off or accidentially due to power failure, the biasing spring 35 will rotate the lever counterclockwise which in turn will cause the spring coil 27 to wind about and turn the motor shaft 21, and the power roll shaft 25 as well, in a reverse direction until the other end 29 of the spring encounters the bottom of slot 31 forcing the wrap spring to wind more tightly and to grip the motor shaft, thus preventing any further reverse rotation of the motor and power roll shafts. This is the condition shown in FIGURE 1 wherein the counterclockwise biased lever 26 pulls on link 33 thereby holding the key lever locking blade 18 beneath the key lever notches 17, against the pull of a spring 36 secured to the blade 18 and a frame member (not shown), tending to urge the blade 18 counterclockwise for reasons hereinafter apparent. Upon motor energization the shaft 21 will rotate to frictionally drive the coil spring 27 which in turn will rotate the lever 26 clockwise until the end 29 of the spring engages the top of the slot 31 as shown in FIGURE 3, thus relieving the grip of the spring 27 from the shaft to the extent that it slips relative to the shaft. The friction between spring 27 and shaft 21 is sulficient to maintain the lever 26 rotated against the energy stored in and exerted by the lever biasing spring 35. As is evident the clockwise movement of the lever 26 will push forwardly on link 33 thereby permitting the spring 36 to rotate the locking blade 18 counterclockwise from beneath the key levers to permit key lever depression.

The service function key levers, particularly the service function key lever associated with carriage return is not operatively associated with the locking blade for the evident reason that the locking blade is usually operable into locking position as by a pull on a link 37 when the carriage moves against the right margin stop in a manner disclosed in Patent 2,675,902 thereby to prevent overtyping at the end of a typing line. In this condition the carriage return key must be operable to move the locking blade to unlocked condition after the carriage moves away from the right margin in return direction. The slot 38 in tab 34 to which the link 33 is connected to the locking blade is provided to permit movement of the locking blade 18 to locked condition at the end of a typing line without effect on the motor powered blade locking mechanism.

That service function key levers are not locked out by the type action key lever locking blade requires auxiliary mechanism for locking out the service function key levers, particularly where the tripping of associated service function actions when the machine is off, with the consequent operation thereof when the machine is turned on, could cause machine damage.

Where, however, the service function key levers are associated with spring clutch mechanisms of the type disclosed in US. Patent 3,212,616, the locking mechanism hereinabove described is effective to disable the service function clutches such that depression of the service function key levers when the machine is off, will not trip associated clutches. FIGURE 1 shows a service function key level 39, e.g. a carriage return key lever, associated with a wrap spring clutch for coupling power to a carriage return function actuator. More particularly the carriage return function clutch comprises a wrap spring 41 mounted on one end of the power roll shaft 25 having a diameter such as to normally grip the power roll shaft.

One end of the spring 41 is connected to a cam 42 comprising the function actuator which is rotatably mounted on the shaft 25, and the other end 43 of the spring extends upwardly forward of the stop lug 44 on the end of the service function key lever 39 thus rotatably biasing the spring to expanded condition such that the spring is held from gripping the shaft 25 and driving the cam 42 which will drive a follower to effect an associated service function such as back space or carriage return.

Since the power roll shaft 25 is reversely rotated to the extent permitted by the slot 31 in the frame member 32, tension of the service function wrap spring will relax and the spring end 43 will move away from lug 44 when the machine is off as shown in FIGURE 1. Hence should a service function key lever be depressed while the machine is off, the spring 41 being no longer tensioned will not move rearwardly of the stop lug. Accordingly depression of a service key lever when the machine is off will not trip or condition its associated function for operation when the machine is later turned on.

It should be understood that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

The invention claimed is:

1. An electric typewriter having a keyboard including a plurality of service function key levers,

a shaft adapted to be continuously rotated,

wrap spring clutches associated with said key levers connected to service function actuators; said key levers in normal state holding said clutches disengaged and effecting clutch engagement when depressed,

and means for reversely rotating said shaft when its motive source is shut off thereby to disable the key lever clutch connections.

2. A typewriter as recited in claim 1 wherein said keyboard includes a plurality of type action key levers, and a type action key lever locking blade positionable by said shaft reversing means to block type action key lever depression.

3. An electric typewriter as recited in claim 1 further including means responsive to shaft rotation to overcome said shaft reversing means and to store energy therein.

4. In an electric typewriter or like machine having a plurality of key levers depressible to initiate powered type actions and service functions:

a key lever locking blade movable between first and second positions to respectively block and permit de pressions of key levers associated with type actions;

a motor driven shaft adapted to be rotated in a forward direction upon energization of motor means;

means for moving said locking blade into and to maintain said locking blade in said second position in response to forward shaft rotation and to move said locking blade into said first position upon cessation of forward shaft rotation comprising:

a first spring wound on said motor driven shaft in the direction of forward shaft rotation to be frictionally driven upon forward rotation of said shaft,

a lever rotatably supported by said motor driven shaft and connected to one end of said first spring,

a link connecting said lever and said locking blade,

and a second spring, said second spring rotatively biasing said lever to move said locking blade into said first position and to effect engagement of and reverse rotation of said motor driven shaft by said first spring upon cessation of forward shaft rotation, said first spring rotatably driving said lever opposite the spring biased direction when said motor driven shaft is rotating forwardly thereby moving said blade to said second position;

and means positioned to arrest the other end of said first spring after a predetermined angular rotation of said first spring whereby said first spring will slip relative to said forwardly rotating shaft.

5. In an electric typewriter or like machine as recited in claim 4 further comprising a power shaft coupled to said motor driven shaft, a wrapspring clutch wound on said power shaft and coupled at one end to a service function operating cam, said service function key lever normally restraining the opposite end of said wrap spring clutch whereby it is disengaged from said power shaft, depression of said service function key lever releasing said wrap spring clutch end whereby said cam is coupled to said power shaft, said second spring biasing said lever operating to effect engagement of said first spring and motor driven shaft thus reversely rotating said motor driven shaft and power shaft upon cessation of forward shaft rotation, said reverse rotation backing off said wrap spring clutch end from said service function key lever whereby upon cessation of forward shaft rotation, said wrap spring clutch is disabled.

6. In an electric typewriter as recited in claim 5 further comprising means positioned to limit reverse rotation of said first spring by said biasing spring upon cessation of motor rotation thereby to lock said shafts against further reverse rotation.

(References on following page) 5 References Cited 2,903,118 UNITED STATES PATENTS 21919781 2,945,577 11/1930 Degener 197-17 3 212 1 9/1946 Von Reppert 197-107 X 5 3 217,850 6/1950 Holt 197-107 4/1954 Kupper 197-107 X 10/1957 Lambert et a1 197-17 6 Link 197-17 Rix et a1. 197-17 Frechette 197-107 X Frechette et a1 197-17 X Frechette et a1. 197-107 X ROBERT E. PULFREY, Primary Examiner. E. T. WRIGHT, Examiner. 

1. AN ELECTRIC TYPEWRITER HAVING A KEYBOARD INCLUDING A PLURALITY OF SERVICE FUNCTION KEY LEVERS, A SHAFT ADAPTED TO BE CONTINUOUSLY ROTATED, WRAP SPRING CLUTCHES ASSOCIATED WITH SAID KEY LEVERS CONNECTED TO SERVICE FUNCTION ACTUATORS; SAID KEY LEVERS IN NORMAL STATE HOLDING SAID CLUTCHES DISENGAGED AND EFFECTING CLUTCH ENGAGEMENT WHEN DEPRESSED, AND MEANS FOR REVERSELY ROTATING SAID SHAFT WHEN ITS MOTIVE SOURCE IS SHUT OFF THEREBY TO DISABLE THE KEY LEVER CLUTCH CONNECTIONS. 